1. Field of the Invention
The present invention relates to a cervical disk prosthesis.
2. Description of Related Art
Cervical disk prostheses are implants for taking the place of the natural intervertebral disk that lies between cervical vertebrae.
In known manner, these prostheses comprise a top assembly and a bottom assembly, together defining a ball-joint system constituted by at least two plates designed to be anchored in the vertebral plates of two adjacent vertebrae. These plates themselves, or by means of inserts, define a dome, i.e. a convex spherical cap, and a cup, i.e. a concave spherical cap. Co-operation between these two spherical caps constitutes a ball-joint system that conserves relative mobility between the vertebrae that is substantially equal to that provided by the natural intervertebral disk.
Usually, these prostheses are made of chromium-cobalt alloy. That material is entirely biocompatible.
Nevertheless, that material presents the drawback of not being transparent to medical imaging, e.g. by means of magnetic resonance imaging (MRI) or by means of a scanner. The presence in the body of a patient of a chromium-cobalt prosthesis disturbs the image that can be obtained using those techniques.
To remedy that drawback, it is known to use another material, polyetheretherketone (PEEK) that presents very good biocompatibility properties, and that is transparent to medical imaging. Nevertheless, that material presents mechanical properties and suitability for machining that are very different from those of chromium-cobalt.